1. Field of the Invention
The invention relates to an optical sight used for example on a hunting weapon such as a hunting gun. The invention more particularly relates to a sight in which a light source creates a light spot which is superimposed on a target which is viewed through the sight.
2. Description of Related Art
Weapon sights comprising a light channel, a lens at one end of the light channel, having a partially reflecting surface, a light emitting diode (LED), and a battery for energising the light source have been available for approximately 20 years. In these sights, the energised LED emits light towards the reflecting surface of the lens to produce an image of a light spot which can be superimposed on a target when sighting through the light channel from the other end thereof. The intensity of the light spot is varied by altering the drive current of the LED.
The main problem with these sights is low battery life (approximately four hours of continuous use at the brightest spot intensity). As a result, the user must replace the battery at regular intervals. This can lead to various practical problems especially if the user is in some remote location and batteries are not readily available. Further, since the sight can be used in extreme conditions, the battery compartment must be made as a watertight enclosure which can be opened. This adds to production costs and generally reduces the overall robustness of the sight.
SE-B-378 450 and SE-B-449 262 teach that in order to save energy, the LED should be pulsed. Although such an arrangement increases the battery life of the sight, the resulting sight still has a low battery life of approximately forty hours of continuous use at the brightest spot intensity.